The middle atmosphere in winter shows a high interannual variability in polar latitudes. To investigate the coupling between stratosphere and troposphere, the annual variation of Northern Annular Modes (NAMs) and the variability of Polar night Jet Oscillations (PJOs) are examined in ERA-Interim reanalysis. 20 major sudden stratospheric warmings are found by using a NAM threshold of -2.3 at the 10 hPa layer in agreement with former studies. With an extended definition of PJO events we identified 9 strong PJOs and 7 no PJO events. Strong PJOs show a strong downward propagating signal into the middle troposphere after the central day (CD). Significant differences between strong PJOs and no PJOs occur: (i) in the upper troposphere about 20 days before CD, (ii) in the stratosphere and troposphere after CD. In the lower stratosphere the zonal mean zonal wind anomalies are significantly reduced for strong PJOs about 20 days and about 45 days after CD. The zonal mean wind reductions are in coherence with pulses of enhanced eddy heat transport by planetary waves and their induced convergence of EP fluxes. For strong PJOs, the reestablishment of a strong polar vortex with strong zonal mean zonal wind anomalies in the upper stratosphere about 10 days after CD is caused mainly by radiative cooling and reduced upward transport of angular momentum by planetary waves. We show that strong PJOs are odds-on favorite for enhanced coupling between stratosphere and troposphere with potential for seasonal forecasts.